Agorio and Vera (pages 3778–3790) characterize an ocp (for overexpressor of cationic peroxidase) mutant that overexpresses the H2O2-responsive Ep5C promoter fused to the β-glucuronidase reporter gene. The ocp11 mutant exhibits enhanced disease susceptibility to several virulent and avirulent strains of the bacterial pathogen Pseudomonas syringae. OCP11 was cloned and found to encode ARGONAUTE4 (AGO4), a component of the pathway that mediates the transcriptional gene silencing associated with siRNA. Another mutant allele, ago4-1, was examined and likewise found to be compromised in resistance to P. syringae. Surprisingly, AGO4 was found to function independently of other components of the AGO4-dependent gene silencing pathway in conferring resistance to P. syringae strains, possibly due to functional redundancy of the other components. In addition, the authors found that transcriptional activation of the reporter gene was correlated with demethylation of specific sites in the promoter region and that methylation of this promoter was altered following bacterial infection. This suggests that that demethylation of specific (as yet unidentified) host genes might be an important component of AGO4 involvement in modulating disease resistance. This work provides additional insight into and support for the notion that the small RNA gene silencing pathway is involved in resistance to bacterial pathogens.